Commercial/residential entry and garage doors are typically produced by filling a cavity within a door (“door cavity”) with various materials. One such material is polyurethane foam. The polyurethane foam improves the thermal and/or acoustic insulation properties of the door and also functions as a structural adhesive thereby improving the durability of the door.
A shell of the door (“door shell”) typically defines the door cavity. To fill the door cavity with the polyurethane foam, a polyol, an isocyanate, and a blowing agent are combined to form a reaction mixture. The door shell is inserted into a press, and the reaction mixture is injected into the door cavity. Once injected, the reaction mixture contacts an inner surface of the door shell, is dispersed within the door cavity, and forms the polyurethane foam through a polyol-isocyanate reaction. The press restrains the door shell and prevents warping when the door cavity is filled with the polyurethane foam.
The area of the inner surface of the door shell which is initially contacted by the reaction mixture is known in the art as a “wet area”. Polyurethane foams are known to exhibit poor adhesion in the wet area. That is, an adhesive bond between the polyurethane foam and the door shell tends to be weak and often results in delamination of the door shell from the polyurethane foam. Such delamination negatively impacts both the acoustic and the structural properties of the door.
In view of the foregoing, there remains a need to further improve upon existing polyurethane foams which are used to form composite articles such as doors. More specifically, there remains a need for a polyurethane foam which exhibits improved adhesion to various substrates and the wet areas thereon.